Magnetic plate cylinder



1970 E. 0. NYSTRAND 3,49

MAGNETIC PLATE CYLINDER Filed March 29. 1968 Fl G.|

'n mm mm mm I6 I9 I INVENIOR.

I ERNST DANIEL NYSTRAND v fi yw United States Patent 3,496,866 MAGNETIC PLATE CYLINDER Ernst Daniel Nystrand, Green Bay, Wis., assignor to Paper Converting Machine Company, Inc., Green Bay, Wis., a corporation of Wisconsin Filed Mar. 29, 1968, Ser. No. 717,136 Int. Cl. B411? 13/08 US. Cl. 101-378 3 Claims ABSTRACT OF THE DISCLOSURE The magnetic plate cylinder has a plurality of axiallyspaced, aligned permanent magnets, interspersed with pole pieces. The pole pieces project radially outwardly beyond the permanent magnets and are contoured to conform to the surface of the cylinder. The entire assembly of pole pieces and permanent magnets is held together with an epoxy resin adhesive within a channel-shaped member positioned with a conforming axially-extending slot in the surface of the plate cylinder.

Background of invention The conventional way of making magnetic plate cylinders is to use washers of soft iron as pole pieces alternating with washers of permanent magnets on a cylindrical Steel body with suitable journals for bearings-and with driving means. The magnets are assembled so that like poles are against each pole piece. The most powerful magnets today are made of ceramic material which, because of its extreme hardness and brittleness, is very difficult to machine. It is therefore customary to eliminate the machining and use epoxy to fill the void. The magnet washers may be in one piece or in segments while the steel washers usually are of one-piece construction. If the steel body is made of an alloy that is capable of magnetic attraction, it has to be insulated from the washers usually by means of bronze bushings between the steel body and the washers. For maximum efiiciency, it is important that there is contact between magnets and pole pieces. Variation and thickness of magnets makes this impossible except in a few spots. The assembly of all of these parts with careful application and curing of the epoxy is a time-consuming, costly and inefficient operation. As the body of the roll has to be substantially smaller in diameter than the outside diameter of the assembled and finished roll, one has to contend with the loss of stiffness in the roll which is apt to cause undesirable deflection and bounce when printing.

As the steel backing material of theplate is very thin, on the order of about 0.007" to about 0.011", the pole pieces and magnets also have to be very thin for maximum holding flux. Any loss of flux is apt to cause insufficient holding power at the leading and trailing edges of the printing plate, causing these edges to bend outward.

Summary of the invention The invention is embodied in a novel construction wherein pole pieces and magnets are pre-assembled into channel members which fit into slots in the plate cylinder body, held down by screws and subsequently turned and ground with the cylinder. The channel itself may be made of brass, aluminum or non-magnetic stainless material for adequate shielding or insulating of the flux from the steel body to get maximum flux from pole piece to pole piece through the thin-plate backing. Through this construction, the important aspect of having the magnets and pole pieces positioned at right angles to the axis of the channel for maximum efficiency is achieved.

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Detailed description of the invention The invention is explained in conjunction with an illustrative embodiment in the accompanying drawing, in which:

FIG. 1 is an elevational view, partially broken away, showing a plate cylinder constructed according to the invention;

FIG. 2 is an enlarged sectional view such as would be seen along the sight line 2-2 of FIG. 1;

FIG. 3 is a fragmentary plan view such as would be seen along the sight line 3-3 applied to FIG. 2; and

FIG. 4 is a fragmentary sectional view taken along the sight line 4-4 of FIG. 3.

In the illustration given and with reference to FIGS. 1 and 2, the numeral 10 designates generally a plate cylinder which is seen to be equipped with the usual journals 11. The surface of the cylinder is interrupted with axially elongated slots as at 12, 13, etc. (see FIG. 2) for the receipt of magnetic insert devices generally designated 14 and 15. The invention is concerned only with the type identified as number 14 and seen in greater detail in FIGS. 3 and 4. In brief, the difference between the magnetic hold down means illustrated at 14 and 15 resides in the direction of polarity of the magnetic members. In the type illustrated in FIGS. 3 and 4, it is seen that the permanent magnets have their longer dimensions perpendicular to the axial length of the cylinder to set up a flux as at F in FIG. 4 extending longitudinally or axially of the cylinder. The type of hold down means at 15 is intended as an intermediateholddown support and has its flux extending in a direction circumferentially of the cylinder 10.

In any event, the construction utilized here is in studied contrast to that characteristic of the prior art wherein circular washers were employed for at least the pole pieces and in many instances for both the pole pieces and the permanent magnets. An improvement on that type of construction may be seen in the co-owned, co-pending application of Ross C. Meade and Charles J. Sanders, Ser. No. 610,176, filed Jan. 18, 1967, now Patent No. 3,438,324.

The member 14 is seen first to include a generally channel-shaped member 16 which, as pointed out before, is constructed of flux-insulating material such as brass, aluminum, non-magnetic stainless steel, etc. In the use of the term channel-shape, I do not mean to be restrictive since trapezoidal, dove-tails and the like may be equally advantageously used. Initially, the channel 16 is prepared independently of the roll 10. The roll 10 merely is equipped with a suitable slot or slots as at 12 for the receipt of the finished channel member. The channel member includes a plurality of permanent magnets as at 17 and 18 (see FIG. 4). These magnets are installed with like poles in adjacent relationship. Between the like poles is inserted a pole piece 19 and the assembly of the plural ity of pole pieces and magnets is adhesively secured together by means of an epoxy as at 20. At suitable positions along the length of the channel 16, the completed element is bored as at 21 for the receipt of a securing bolt as at 22 (see FIGS. 3 and 2, respectively).

In operation, a steel-backed printing plate may be installed on the cylinder with the leading edge 23 and the trailing edge 24 having irregular contours (see dark-dot lines, FIG. 3). Thus, the width of the channel member (after grinding) should be of an extent sutficient to accommodate such contours. The grinding is indicated relative to the insert 14 in the lower right-hand corner of FIG. 2 where the dotted portion 25 has been ground off to the contour of the cylinder.

I have found that to get the desirable flux configuration F seen in FIG. 4, i.e., limiting the flux path to a space immediately above the pole pieces, relatively thin magnets and pole pieces should be employed. Optimum results are obtained with the pole pieces of the order of A in width and the permanent magnets of the order of /8" in thickness. Larger dimensions can be tolerated although for best results I prefer to have at least three pole piece magnet combinations per lineal inch, i.e., measured axially along the cylinder 10.

With the inventive construction, numerous advantages accrue over the washers or rings previously employed. A much stronger and stiffer roll results, along with the ease of assembly, which limits the undesirable deflection or bouncing mentioned previously. Also, a greater flux density is achieved since with the arrangement specified, substantial contact can be achieved between the pole pieces and permanent magnets which is not characteristic of the prior art construction.

In some instances, I may provide an elongated slot as at 26 to further aid in the alignment of the leading and trailing edges of the printing plate.

I claim:

1. In a printing cylinder for use with thin, steel-backed plates and the like, a plate cylinder having an axial slot in the periphery thereof and with the slot having a circumferential extent sufiicient to have both axial edges of said plate contact said slot, a unitary insert in said slot, said insert comprising a generally channel-shaped member received in said slot and constructed of flux insulating material, a plurality of permanent magnets in said member, each magnet lying traverse of said cylinder axis of said cylinder axis and said plurality of magnets being aligned in spaced apart relation axially of said cylinder axis, a rn'agnetizable element between adjacent magnets and projecting radially outward of said magnets, said magnets assembled so that like poles are against opposite sides of each of said magnetizable elements, and .a hardened adhesive connecting adjacent elements to provide said unitary construction, the outer surface of said insert being contoured to the surface of said cylinder, and means securing said insert to said cylinder.

2. The structure of claim 1 in which said insert mag-. nets and projecting elements are arranged in pairs with the thickness of the magnets and elements being so constructed as to have more than three pairs of said magnets and elements per lineal inch.

3. The structure of claim 2 in which said projecting elements have a thickness of the order of about 5 and the magnets have a thickness of the order of about /3.

References Cited UNITED STATES PATENTS 2,952,205 9/1960 Dunwoodie l01378 3,039,389 6/1962 Meese et al 101-378 3,097,598 7/1963 Hotop et al. 101-378 3,180,259 4/1965 McKay 101-378 ROBERT E. PULFREY, Primary Examiner J. R. FISHER, Assistant Examiner 

